Thank you so much, Jeff, for really pushing this thread - I had thought the banter issue had been a design choice at first, and I had been incredibly disappointed how silent the game was. I know party banter isn't an urgent game breaking bug, but I feel that it is a strong narrative breaking bug. Considering the new story structure of DAI in comparison to DAO/DAII (main quest + Haven/Skyhold interaction + exploration/fetch quests), a large portion of the story is delivered via your companions. So much of the companions character development (especially in DAII) was heard through banter, so it leaves DAI feeling hollow in comparison to the last two. I think I'm thirty hours in, and I'm tossing up restarting - I don't really want to spend the next thirty hours in predominantly awkward silence! I'm on PS4 with a physical disc (it's been running beautifully otherwise, I've been really surprised how well it has gone), so I will try the data reinstall as mentioned above.
I've tried everything I can think off re: banter triggers. I've tried keeping the same parties together, I've tried mixing it up a lot as well. I had been concerned that the problem was my unique mountain rock climbing skills (and awkward abseiling thereafter), but after spending hours sticking to paths, that hasn't helped either. I've stood idle for minutes at a time - no dice. Exploring areas of the map I've never been doesn't help, re-treading areas I've already been also doesn't help.
Fallow Mire: x2 (would only fire for Sera/Blackwall) - 3hrs there?
Storm Coast: 0 (have tried multiple party combinations.) 4hrs?
Forbidden Oasis: 0 - 1hr.
Hinterlands: x8? - 16 hrs? Hinterlands is odd, because I have had some banter, but for the amount of time I've spent in the Hinterlands, it's fairly miniscule. (The following mentions are so specific because I was genuinely shocked anytime someone talked!) I've had two Cass/Varric interactions early on, and then Solas/Varric near Solas' early quest. One Cass/Viv whilst I was half-way up a cliff. I think Cole/Blackwall may have triggered on a path near a camp, and a Solas/Blackwall near Redcliffe Village. After getting to Skyhold and finally getting Dorian (nearly 30hrs in), I took him to the Hinterlands and started mucking around in the very top left of the map. To my absolute astonishment, Dorian/Sera started up; then a minute later Dorian/Iron Bull; then about three minutes later Sera/Iron Bull. The banter is so fantastic when it works! It makes the world seem alive. Alas, they then descended into sulky silence and from then on refused to talk again.
Sadly, the lovely Vivienne pretty much refuses to banter with anyone outside Cass (how in character)! I used her for the Storm Coast/The Fallow Mire (good six hours) with Sera/Blackwall, and nothing triggered with them despite all the dialogue she is supposed to have with both. Cole and Bull don't talk much either, whereas Sera, Dorian and Blackwall seem to be the best at triggering banter - Sera obviously in particular. Companions have no problems reacting to the world (ie. discovering an area/item, an anecdote or two, enemy warnings), but won't talk to each other. I'm not remotely knowledgeable in game design, let alone programming, but could it be some sort of priority banter bug - do they companions know they're allowed to speak? Sera can't stop, Vivienne won't start. Obviously, none of them are doing it remotely enough.
The only other glitches I've had have been dialogue wheel related - were you have to press L1 or skip through with square. Dorian got it quite bad in his first convo at Skyhold (lots of mutual prolonged staring), I also don't know if remotely related.
Out of curiosity, how often are people getting musical cue triggers? (I've been assuming the music is trigged by moving into sub-areas within the regions, and isn't randomised?) I feel like 97% of my exploration is spent in silence, with just ambient background noise. (The Fallow Mire I think has had the most music, I'm assuming due to its smaller size?) Skyrim didn't use music all the time, either, but I feel like at least 50% of my time with Skyrim was accompanied by some kind of music. It leaves DAI feeling quite claustrophobic, actually. The phenomenal level design in each region is at least enough to make it bearable, but it still feels quite hollow.
If it helps - Male Qunari Inquisitor, warrior, American voice, imported world state, physical PS4 disc. I also have Flames of the Inquisition, and the bizarre Red Templar weapons. (I'd like to add that I'm really sympathetic to the poor devs, I can't imagine how much of a pain it could end up being to fix the banter issue, if they can fix it at all.) Yikes, this ended up being really long, sorry, guys.